Method and Positioning System for Determining a Region to be Examined in a Subject

ABSTRACT

A method and positioning system for determining a region to be examined in a subject on a movable support of a medical imaging system. The method includes: a) manually specifying the region by positioning a predetermined marker object in relation to the subject; b) acquiring the position of the marker object by an acquisition apparatus; c) projecting or displaying a feedback marking by a projection apparatus at the acquired position on the subject, wherein the position of the marker object and the acquired position are adjustable; d) calculating a scan position of the movable support on the basis of the acquired position by means of a computer unit, wherein in the scan position, the region to be examined is arranged in an acquisition region of the imaging system; and e) automatically moving the movable support into the scan position with a motor.

TECHNICAL FIELD

The present disclosure relates to a method for determining a region tobe examined in a subject, a method for determining a field of view for ascan, a method for training an artificial neural network for determininga field of view and a positioning system for determining a region to beexamined in a subject.

BACKGROUND

An examination in a medical imaging system, for example, in the contextof magnetic resonance tomography (MRT), computed tomography (CT) or MRTpositron-emission tomography (MRT-PET) typically requires a medicaltechnical assistant (MTA) position the patient on the patient supportand then to ensure that the support is correctly positioned in theimaging system. For example, a laser beam can be directed at a fixedposition on the patient, and the MTA moves the support manually to aposition in which the laser beam points to the desired site on thepatient. Once the desired site on the patient has been established, thesupport automatically moves with this site into the isocenter of thesystem. It is also known to communicate a support position and/or a siteof the support to the system by numerical input. The isocenter is, inparticular, the region in the imaging system that is best suited for anexamination, for example, the region where the magnetic field of an MRTdevice is sufficiently homogeneous for imaging.

The previous approaches, however, require a certain amount of time, areoften not intuitively usable and/or are sometimes very cumbersome.Sometimes, very heavy demands are made on the precision of thepositioning, which in procedures known from the prior art cannot alwaysbe entirely met.

SUMMARY

It is therefore an object of the disclosure to provide a method and asystem with which the positioning of a movable support with a subjectlying thereon can be communicated to an imaging system quickly, easilyand precisely.

According to a first aspect of the disclosure, a method for determininga region to be examined in a subject, in particular a patient, on amovable support of a medical imaging system, is provided. The methodcomprises the steps: a) manually specifying the region by positioning apredetermined marker object in relation to the subject; b) acquiring theposition of the marker object by means of an acquisition apparatus; c)projecting and/or displaying a feedback marking by a projectionapparatus at the currently acquired position on the subject andoptionally adjusting the position of the marker object and the currentlyacquired position; d) calculating a scan position of the support on thebasis of the acquired position by means of a computer unit, wherein inthe scan position, the region to be examined is arranged in anacquisition region of the imaging system; e) automatically moving thesupport into the scan position with a motor. The disclosure canadvantageously enable a region to be examined to be specifiedintuitively and with relatively little effort by the user. Therein, aparticularly rapid and simultaneously exact positioning technique can beenabled. By way of the feedback marking, a feedback mechanism canfurther be enabled which can, on the one hand, enable a more reliableinput and, on the other hand, can increase the trust of the user in thismethod. In particular, a medical workflow can thereby be particularlyefficient and rapid.

The region to be examined can be, in particular, a site on the body ofthe patient. For example, the region to be examined can be a position inthe longitudinal direction of the support. Thus, the region to beexamined can be defined by a position on a one-dimensional scale. It isalso conceivable that the region to be examined is defined in atwo-dimensional plane, in particular, a plane parallel to the support,or that it is a three-dimensional region. In advantageous aspects, theregion to be examined is determined through exactly one position and/orexactly one point, but can also have a one, two or three-dimensionalextent. The region to be examined can be, in particular, a site on thesurface of the subject, in particular on the body surface of thepatient. It is alternatively also conceivable that, for example, bymeans of directional gestures, a region is identified which is situatedwithin the subject, in particular, within the patient body. The regionto be examined can be associated, for example, with a body part and/oran organ or can comprise the body part/the organ. During the method, itis preferably provided that the subject is situated lying on thesupport. Preferably, the subject therein moves as little as possible inrelation to the support. The support can preferably be movable at leastin its longitudinal direction. In particular, the support can be movedin and out of an examination region or a scan region of the imagingsystem. It is also conceivable that the support can also be movable in adirection perpendicularly to its longitudinal direction. In this regardand as described below, the longitudinal direction of the support can bedesignated the z-direction, a transverse direction of the support whichis perpendicular to the z-direction and is substantially parallel to thesupport area, can be designated the x-direction and a directionperpendicular to the support surface as the y-direction. The medicalimaging system can be, in principle, any imaging system which comprisesa movable support and an, in particular stationary, examination region.Alternatively, the support can also be stationary and the imaging systemcan be movable in the z-direction. For example, the imaging system canbe a magnetic resonance tomography (MRT) system, a computed tomography(CT) system or an MRT positron emission tomography (MRT-PET) system. Thecomputer unit can be part of a control computer of the imaging system ora separate computer.

A manual input should be understood, in particular, to be input by auser or an operating person, for example, a medical technical assistant.The marker object can be, in principle, any object that is recognizableby the acquisition apparatus. In particular, the marker object can be abody part of the user or an object that is accessible to or movable bythe user. In this context, predetermined preferably means that themarker object or its shape or appearance is stored in the acquisitionapparatus or in a connected evaluating apparatus, so that, inparticular, an image alignment between the marker object and a storedpattern can take place. The user can orient themself to the position ofthe subject and the region to be examined on the subject and can thusalign the marker object directly in relation to the subject. This canenable, in particular, a direct and intuitive specification of theregion. The acquisition of the position can mean, in particular, theacquisition of a predetermined portion of the marker object. Forexample, the tip of a rod or the outstretched fingertip of a user can beacquired. The position can be understood, in particular, to be a spatialcoordinate. Alternatively or additionally, however, a spatialorientation of the marker object, for example, a rotary direction, canalso fall under the definition of position.

With regard to the acquisition of the position, the marker object can bepassive, active or independent. The acquisition apparatus which acquiresthe position of the marker object can itself be arranged on the markerobject. For example, a position sensor and a transmitter apparatus canbe arranged on the marker object (independent acquisition).Alternatively, the acquisition apparatus can also be arranged remotelyfrom the marker object, for example, in the form of a camera which canacquire the marker object and a computer unit which can determine theposition of the marker object from the camera image (passively).According to a further alternative, the acquisition apparatus can bearranged both partially on the marker object and also partially remotelyfrom the marker object, for example, in the form of an infraredtransmitter and receiver remote from the marker object and aretroreflector on the marker object. In principle, the combination of aplurality of (also different) acquisition apparatuses is alsoconceivable. This can enable, for example, a greater precision and/or agreater reliability to be achieved.

The projection and/or display of a feedback marking can enable the user,in particular, to recognize immediately whether the acquired positionactually corresponds to the region envisaged by the user. In thisregard, “at the currently acquired position” can mean, in particular,that the feedback marking is adjusted to a changing position of themarker object immediately or as quickly as possible. For example, it canbe provided that, starting from the displayed feedback marking, the useradjusts the position of the marker object until the feedback marking ismarked as precisely as possible or as necessary to the region to beexamined. The feedback marking can preferably be a projected geometricform or a pattern which is suitable for displaying a position or aregion. For example, the feedback marking can be a projected cross, aprojected point, a 3D box or a suitably designed form. The system isconfigured to calculate a scan position by means of a computer unit. Thescan position can preferably be a position of the support in which theregion to be examined is or would be situated, in particular, in anacquisition region. For example, the scan position can be defined bymeans of the z-coordinate of the support. In addition, the scan positioncan optionally comprise the y-coordinates and/or the x-coordinates. Theacquisition region can preferably be that region in which the imagingsystem, in particular, an imaging device or a scanner unit of theimaging system, can scan or can scan particularly well. For example, theacquisition region can correspond to the isocenter of the imagingsystem, can lie in the isocenter or can be arranged around theisocenter. For example, the imaging system can be configured to acquirethe current position of the support automatically and, by comparisonwith the acquired position of the marker object, to ascertain how thesupport must be moved in order to bring the region to be examined intothe acquisition region. The position of the support needed therefor cancorrespond, in particular, to the scan position. The system can then beconfigured, in particular, to move the support automatically into thescan position by means of a motor. The motor can be controlled, forexample, by the computer unit or by a further computer unit of theimaging system. Preferably, the motor is a motor that is designed foroperation in a magnetic field. Alternatively or additionally, it isconceivable that the motor is arranged externally, in particular,outside a scan region or the acquisition region. An interaction with themagnetic field of the imaging system can thereby be prevented orreduced.

According to one aspect, the feedback marking can be generated with alight source, in particular a laser, arranged over the support, whereinthe light beam generated by the light source, in particular the laser,is incident at the acquired position at least substantially verticallyon the object. This can be achieved, for example, in that the lightsource, in particular the laser, is movably arranged by means of a railon the ceiling of the treatment room or on another fastening facilityover the support. Preferably, the rail can extend along the longitudinaldirection of the support or along the z-axis. In particular, the lasercan be movable automatically by means of a motor along the rail parallelto the longitudinal direction of the support. Through a verticalincidence, a parallax error of the feedback marking can be reduced orprevented. A parallax error could cause the feedback marking to appeardistorted or obliquely curved. Furthermore, in particular, if the heightof the subject is not considered, the feedback marking could appear at afalse position, in particular z-position. Substantially vertical meanstherein that smaller deviations, i.e. a slightly oblique position, e.g.±10°, preferably ±5°, more preferably ±1°, could possibly still beacceptable in the context of this aspect. In particular, it can beprovided, for example, that the direction of the incident light beam, inparticular laser beam, has substantially no z-component, but a smallx-component. This means that it can be provided that the light beam, inparticular, the laser beam is incident substantially perpendicularlywith regard to the longitudinal direction of the support, but withregard to the transverse direction of the support, has a deflectioncorresponding to the width of the support and the height of the mountedlight source, in particular the mounted laser.

According to one aspect, it can be provided that the feedback marking isgenerated with a light source arranged over the support, in particular alaser, wherein the light beam, in particular the laser beam, is divertedwith mirrors such that the light beam, in particular the laser beam, isincident at the acquired position at least substantially vertically onthe object. The light source, in particular the laser, can therein bearranged at a fixed position in the z-direction, preferably centrallyover the support. Through the diversion with mirrors, a substantiallyvertical incidence can be enabled in the entire longitudinal extent ofthe support without the light source itself, in particular the laser,needing to be moved in the z-direction.

According to one aspect, it can be provided that the light source, inparticular the laser, generates a light beam, in particular a laserbeam, with a beam direction lying in a horizontal plane, wherein thelight beam generated, in particular the laser beam, is incident upon aparabolic mirror, in particular a flat parabolic mirror, wherein thefocal point of the parabolic mirror coincides with the position of thelight source, in particular the laser, so that the light beam, inparticular the laser beam, is reflected a first time in the horizontalplane and perpendicularly to the longitudinal direction of the support,wherein the light beam, in particular the laser beam, is reflected asecond time by a flat mirror arranged in the horizontal plane in frontof the parabolic mirror such that it is deflected vertically in thedirection of the support. A horizontal plane is, in particular, a planewhich extends in the (x,z)-direction or extends substantially parallelto the support surface of the support. Through the placement of thelight source or the laser in the focal point of the parabolic mirror,all the light beams or laser beams emerging from the light source or thelaser are reflected parallel to the central axis of the parabolicmirror. In other words, it can be ensured that all the light or laserbeams reflected by the parabolic mirror extend substantially parallel tothe x-axis and substantially perpendicularly to the y-axis and thez-axis. The parabolic mirror can be defined, in particular, by aparabolic formula where

X=a×z ²

and the focal length

$f = \frac{1}{4 \times a}$

For example, the parameter a can have a value of 15 cm⁻¹ to 35 cm⁻¹,preferably 20 cm⁻¹ to 30 cm⁻¹, and the support can have a length of 1.60m to 2.50 m, preferably 1.80 m to 2.20 m. In particular, for a parametervalue a of 25 cm⁻¹ and a length of the support of 2 m, the focus pointcan be provided at a distance of

$f = {\frac{1}{4 \times 0.25m^{- 1}} = {1m}}$

from the apex of the parabolic mirror. A flat parabolic mirror can havethe advantage that it can be produced more cheaply and/or more easilythan a mirror curved in two directions. In addition, with a flatparabolic mirror, space over the support can be saved. The parabolicshape of the flat parabolic mirror is preferably arranged parallel tothe horizontal plane, while the mirror is planar in the verticaldirection. The flat parabolic mirror can be held, for example, by aframe, in particular, a frame the extension direction of which liessubstantially in the horizontal plane, wherein the frame has only asmall extent, in particular, in a direction perpendicular to thehorizontal plane, in particular, an extent of the order of magnitude ofthe corresponding extent of the flat parabolic mirror. For example, itcan be provided that the frame extends in the y-direction approximatelyat least exactly as far as, and not more than 20% further than, theparabolic mirror. Advantageously, an element generating a light patterncan be arranged between the light source or the laser and the parabolicmirror, in particular directly in front of the laser, wherein theelement generating the light pattern is configured, in particular, togenerate the form of the feedback marking from the light or laser beam.For example, the element generating the light pattern can be adiffractive optical element (DOE). A DOE is, in particular, an opticalgrating at which the laser beam is diffracted, for example, a glasssubstrate with a photolithographically applied microstructure, so thatthe laser beam is given the shape of the feedback marking. For example,by means of the DOE, both a pattern and also a beam divergence can beset. It can be provided to emit the laser beams emerging from the laserslightly tilted in the y-direction, for example, by an angle of 1°-10°,preferably 1°-5°. The parabolic mirror and/or the flat mirror can befastened, for example, on the ceiling. Alternatively or additionally,the parabolic mirror and/or the flat mirror can be fastened to afastening means, for example, a frame or a gantry, over the support. Forexample, the flat mirror can be arranged directly above or below thelight source or the laser. It is also conceivable that the flat mirroris arranged, in relation to the parabolic mirror, directly behind thelight source or the laser and nevertheless extends in the verticaldirection or the y-direction above and/or below the light source or thelaser than the light source or the laser. Alternatively or additionally,it can also be provided that the flat mirror is a semi-transparentmirror, wherein the flat mirror is arranged, relative to the parabolicmirror, in front of the light source or the laser. It can be provided,in particular, to generate the incidence point of the feedback markingin the z-direction such that the light source, in particular, the laseror the beam direction of the light beam emitted by the light source, inparticular, the light beam emitted by the laser is rotated, inparticular automatically, about a vertical axis or about the y-axis.

In particular, it can be provided that the position of the feedbackmarking is adjusted in the longitudinal direction of the support in thatthe light source, in particular the laser is rotated in the horizontalplane by means of a first motor controlled by the computer unit.Preferably, the first motor can be a motor that is designed foroperation in a magnetic field. For example, an ultrasonic motor, an MRcompatible stepper and/or servo motor, a pneumatic motor or a hybriddrive can be provided. In addition or alternatively, the position of thefeedback marking can be adjusted in a transverse directionperpendicularly to the longitudinal direction of the support, inparticular the x-direction, in that the flat mirror is rotated aboutitself by means of a second motor controlled by the computer unit aboutan axis parallel to the longitudinal direction of the support.Advantageously, the second motor can be selected according to the sameaspects as the first motor. A deflection in the x-direction can beadvantageous, in particular, in order to be able to specify or visualizean x-coordinate. For example, thereby a field of view, in particular ofa first localizer can be visualized.

According to a further aspect, it can be provided that the feedbackmarking is generated with at least one light projection apparatus, inparticular a video projector, arranged above the support and orientedtoward the support, wherein the light projection apparatus comprises, inparticular, a light source, a collimation optical system, an imageformation unit and a projection optical system. The light source can be,for example, a laser, an LED and/or a lamp. A collimation optical systemis, in particular, an apparatus which influences light beams such thatthey extend parallel. The image formation unit can be, in particular,statically (for example a diffractive optical element (DOE), slide orgobo), dynamic (for example a digital light processor (DLP) or liquidcrystal on silicon (LCoS)) or dynamically transmissive (e.g. LCD). Theimage formation unit can serve, in particular, to shape or form thefeedback marking as, for example, a cross. The projection optical systemcan comprise, in particular, mirrors or a mirror system for divertingthe beams. The feedback marking is generated with at least one videoprojector arranged above the support and directed toward the support.The video projector can be configured, for example, to correct aparallax error digitally by adjusting the projected image. In additionor alternatively, it can be provided that the at least one videoprojector is movable on a longitudinal axis parallel to the longitudinaldirection of the support. The video projector can be oriented, inparticular, vertically or in the y-direction. For example, the videoprojector can be fastened on the ceiling or on a gantry or frame abovethe support. Advantageously, it can be provided to displace the videoprojector automatically for specifying the position of the feedbackmarking in the longitudinal direction of the support along thelongitudinal axis of the support, in particular on a rail or linearaxis. The displacement can be controlled, for example, by the computerunit or by a further computer unit and by means of a drive, inparticular a motor, wherein the motor can be configured, in particular,to be operated in a magnetic field. It can also be provided to provide aplurality of projectors for generating the feedback marking. Forexample, it can be provided to use different colors for the feedbackmarking. Advantageously, the video projector can also enable complexpatterns, in particular 3D images, to be generated. For example, it canbe provided that by means of the video projector, a 3D image isprojected, in particular, by means of augmented reality (AR)/HoloLenseffect, onto the surface of the subject. The 3D image can be, forexample, an FOV box which specifies a scan region, in particular for afirst test scan or a localization scan. For example, it can also beprovided to have the 3D image appear entirely or partially in thesubject. For example, it can be provided that a user, in particular amedical technical assistant observes the 3D image with 3D glasses, inparticular 3D shutter glasses or polarizing glasses. In addition, it canbe provided that a surface, in particular, a blanket that isparticularly suitable for the reproduction of the projection is arrangedon the subject. For example, the surface can be chromatically uniform,in particular, white and/or can have a surface suitable for theprojection of polarized light, in particular, an even smooth surface.

According to one aspect, it can also or alternatively be provided thatthe subject is monitored with a camera, in particular a 3D camera or acombination of a plurality of 2D and/or 3D cameras. The camera can be,for example, a 2D camera or a 3D camera. A combination of a plurality of2D and/or 3D cameras is also conceivable. A 2D camera can, inparticular, be relatively more economical and possibly havesignificantly higher resolution than a 3D camera. The 2D camera can beconfigured, in particular, to acquire the x and z-coordinates, forexample of the fingertip. For example, the camera can be directedvertically downwards. A vertically downwardly directed 2D camera is, inparticular, especially well suited to acquiring the x and z-coordinates.A 2D image can be ascertained, in particular, with known techniques ofimage processing. For example, two images can be recorded with the 2Dcamera, in particular, an image without the pointing hand and a furtherimage with the hand. A difference between the two images can be used toobtain a mapping of the hand. Preferably, the hand of the user pointingto the patient can always be directed, seen from above, substantiallyalong the x-axis, in particular, regardless of which table side the useris situated on. In this case, the fingertip can always be, inparticular, the (X,Z)-point that is closer to the z-axis than all theother points of the difference image. A 3D camera can enable a recordingin three spatial directions, in particular including the y-direction. Acombination of a 3D camera and a high-resolution 2D camera can beparticularly advantageous. It can be provided that the 3D camera isconfigured so that the presence of the pointing hand can be detected in3D with the 3D camera and thereupon, the image recording and evaluationof the image differences with the 2D camera can be triggered. They-coordinate of the fingertip can therein always be ascertained with the3D camera. For example, the y-coordinate can have an accuracy of+/−(5−20) mm, preferably approximately +/−10 mm. The x and z-coordinatesof the fingertip can be, particularly for position determination, moreimportant than the y-coordinate. With the 2D camera, an accuracy of+/−(0.2−3) mm, preferably +/−1 mm can be capable of being ascertainedfor the (x,z)-coordinates. Advantageously, an accuracy of this type, inparticular, in association with the optical feedback, can suffice toplan, for example, a surgical intervention. For example, the 3D cameracan be used to carry out a parallax correction, in particular with thecomputer unit. In particular, it can be provided that, by means of the3D camera, the height of the subject is determined at the acquiredposition, wherein by means of a computer unit, a parallax correction ofthe generated feedback marking is carried out. In particular, acorrection of the feedback marking in the longitudinal direction of thesupport, in particular in the z-direction, and/or in a verticaldirection, in particular in the y-direction, can be carried out. Forexample, it can be provided that the video projector is mounted and/orstatically fixed at a site above the support, in particular is notmovable in the longitudinal direction, and a parallax error on the basisof images of the subject and/or the support acquired by the 3D camera iscorrected by the computer unit or a further computer unit. The 3D cameracan be based, for example, on a stereoscopic acquisition, wherein thecamera comprises, in particular, two lenses. Alternatively, the 3Dcamera can also be based on an encoding of a projected pattern wherein,on the basis of the distortion of the pattern on the acquired object,the three-dimensional topography of the acquired object can bedetermined. A time-of-flight-based 3D acquisition is also conceivable,wherein the camera comprises a projector which emits light, wherein onthe basis of the time of flight of the reflected light, athree-dimensional position in space can be determined. Alternatively, aprojection of stripes of differing width is conceivable, by means ofwhich the three-dimensional position can be ascertained. Advantageously,the 3D camera can be firmly mounted or fixed statically above thesupport. Alternatively, it is also conceivable that the 3D camera ismovable, for example, together or simultaneously with the videoprojector, on a rail, in particular in the longitudinal direction.Advantageously, a movement capability of the 3D camera can be used inorder to acquire or to be able to acquire different views of thesubject. For example, it can be provided that the 3D camera is moved ona linear axis, in particular parallel to the longitudinal direction ofthe support, wherein the camera records different views of the subjectand assembles them into a 3D image, in particular a high-resolution 3Dimage. For example, it can be provided that the 3D camera carries out amovement over the subject and therein records images. Following thecompleted journey, the images can then be combined into an overallimage. Through the movement of the 3D camera, it can advantageously bepossible to reduce the spacing of the 3D camera and the support or thesubject, in particular to 50 cm to 150 cm, preferably to 80 cm to 120 cmand particularly preferably to approximately 1 m, wherein neverthelessthe whole region of the subject can be acquired. The region that can beacquired can typically be restricted by the angle of view of the cameraor of the camera lens, so that by means of the region to be acquired, aminimum spacing from the subject can result, which is necessary in orderto be able to acquire all the sites of the region. This restriction canadvantageously be circumvented by a movable 3D camera. A camera placedcloser to the subject can advantageously enable a higher imageresolution of the overall image or a better effective spatialresolution. For example, image recordings by the 3D camera can be usedto determine subject properties, in particular the size and/or weightand/or shape. Alternatively, by means of the image recordings, theposition or surface coordinates of a local RF coil (radio-frequency coilfor receiving the RF signal) can also be determined; this can be used inMRT-PET combination devices for calculating the attenuation correction,that is, the weakening of the PET image by the RF local coil. A highereffective resolution can enable a more exact determination of theparallax error and/or the position of the marker object. Advantageously,a drive or a drive motor can be selected for the movement of the 3Dcamera according to analog principles such as the motor for the laser orthe mirrors.

According to one aspect which can be combined in particular with one ofthe other aspects, it can be provided that the marker object is a humanhand, in particular a finger, of a user, wherein the position of thehand, in particular the finger, is ascertained by means of a camera, inparticular a 3D camera. For example, it can be provided that a user, inparticular a medical technical assistant, points with their hand towarda site in the subject, in particular, the body of the patient to beexamined. The specification of the region with the hand or the fingercan represent a relatively rapid and simple and also intuitivepossibility for the position specification. For example, the position ofthe hand or the finger can take place with a camera, in particular a 3Dcamera, for example, with the 3D camera described above. The image datacan be used in order to calculate a position, for example(x,y,z)-coordinates. In particular, a position of the fingertip can beascertained automatically. The position can be ascertained eitherdirectly at the camera or the image data can be forwarded to a computerunit for ascertaining the position. It can be provided that the hand orfinger is recognized as the lower end of a cylindrical object, inparticular the arm of the user, with dimensions typical for the humananatomy or is stored as a recognition method in the computer unit.Furthermore, the approximate position of the arm and/or the hand can bestored, for example, as an approximately cylindrical object whichextends from a point beyond the support, in particular from a shoulderobliquely from above to below in the direction of the support or thesubject. With specifications of this type, a particularly reliableacquisition of the hand or the finger and thus a reliable determinationof the position is enabled.

According to a further aspect, the marker object can be a hand-guidedobject, wherein the hand-guided object includes an active, passive orindependent position sensor. For example, the hand-guided object cancomprise an electronic system and/or sensor system for determiningand/or specifying the position. The position can take place inparticular on the basis of the location and/or orientation of the objectin the room. Advantageously, the object can comprise an accelerometerand/or an inclinometer, in particular for determining an inclination ofthe object in order to acquire not only its position, but also itsdirection. For example, the object can also comprise a microcontrollerfor controlling, in particular in the case of an independent or activeposition sensor. The object can optionally comprise an on and offswitch, in particular a button. A switch of this type can advantageouslybe suitable for saving energy. The object can be, for example, a rod (“amagic wand”). Advantageously, the inclination and/or direction of such arod can be detected and thus the “position of the marker object” in thiscase can also be a position which is revealed in the extension of therod, that is, a location to which the user points with the rod. Ahand-guided object can enable an effective and intuitive specificationof the position, wherein at the same time a relatively reliable positiondetermination can be ensured.

In addition or alternatively to one of the other aspects, it can beprovided that gestures with the hand, in particular the finger and/orthe hand-guided object, are used as a position input for the input of afield of view of a scan to be performed with the imaging device and/orfor communicating control commands, in particular with the aid ofprojected operating elements. For example, it can be provided that theoutline of a field of view is drawn in the air. For example, it can beprovided that the input of the field of view for specifying the field ofview (FOV) of a first scan or test scan, in particular, a firstlocalizer is used. In this way, it can be provided, in particular, tospecify both the z-position or the position in the longitudinaldirection of the support and also the x and y-positions or the spatialdirections perpendicular to the longitudinal direction. The FOV can bedefined, in particular, by means of vectors and/or scalars. For example,a vector (x, y, z) can be provided which gives the center of the FOV.This vector can be ascertained, in particular, from the acquiredposition. In addition or alternatively, it is conceivable that gestureson the basis of the temporal sequence of individual, in particularpredetermined, positions are recognized, in particular acquired by theacquisition apparatus and evaluated by the computer unit or aligned withstored predetermined positions. For example, it can be provided that amovement of the marker object toward the subject and holding theposition for a predetermined time, for example 1-2 seconds is acquiredas position input. In particular, by way of the feedback marking, it canbe ensured that the position input is correctly registered.Alternatively or additionally, on the one hand, a singular point can bespecified as a position with the marker object, and also a region, forexample, a circle, rectangle and/or polygon can be specified, inparticular by circling the region. The region can define, in particular,the FOV. Alternatively or additionally, a movement of the marker objectaway from the subject, in particular in the direction of the acquisitionregion of the imaging system can be used as a command for moving thesupport into the acquisition region, wherein in particular, the acquiredposition is moved into an isocenter of the medical imaging system. Theprojected operating elements can be generated, for example, by way of alight projection apparatus, in particular a projector or videoprojector. For example, it can be provided with a projector to projectbuttons or operating elements, for example a green triangle, onto thesupport edge, particularly in reachable proximity of a user. Inparticular, a touch of the projected operating elements, in particularwith the hand as a marker object, can be acquired by means of theacquisition apparatus. The touching of the operating elements cantrigger, for example, an inward movement of the support or othercommands. For example, in addition a touch display can be provided onwhich corresponding or the same operating elements can be displayed.

According to one aspect, the marker object can contain an active,passive or independent position sensor or position sensor element and,for specifying the region to be examined, can be placed on the desiredregion and fastened there on the subject. The marker object cancomprise, for example, an energy store, in particular an accumulator ora battery for operating the position sensor, in particular in the caseof an active and/or independent position sensor. In particular, it canbe provided that a blanket, in particular a warming blanket will be oris placed on the subject, wherein the marker object is fastened on theblanket by means of an adhesive layer or by means of a hook and looparea. The marker object can be fastened, for example, by means of a hookand loop fastener on the subject and/or on the blanket lying on thesubject. In particular, the blanket can comprise hook and loop areas.Alternatively or additionally, a fastening by means of hook and loopfastening can take place also on other objects which are arranged on thesubject, for example, on hook and loop areas on flex coils.Alternatively or additionally, the marker object can comprise, forexample, an adhesive layer for fastening. In particular, the blanketand/or other object can comprise a smooth layer for fastening the markerobject to the adhesive layer. Alternatively or additionally, a fasteningof the marker object can take place by means of belts. For example, thebelts can be fastened form-fittingly and/or frictionally, in particularvia a clip lock on the support. A placement of the marker object on thesubject can enable an intuitive and comfortable specification of theposition, wherein after the placement, the user can optionally attend toother tasks and/or a more thorough examination of the input position.

According to one aspect which, in particular, can be combined with theother aspects, the active, passive or independent position sensor cancontain an illuminated optical retroreflector and/or an opticaltransmitter, wherein at least one 2D camera and/or 3D camera acquiresthe marker object or an ultrasonic or infrared transmitter, wherein theposition of the position sensor is ascertained, in particular, bytrilateration and/or triangulation or a magnetic field sensor, whereinthe imaging device is a magnetic resonance device and the position isdetermined via the strength of the magnetic flux density at the magneticsensor, wherein the strength of the magnetic flux density depends, inparticular, on the spacing from the main magnet of the magneticresonance device. In particular, the strength of the magnetic fluxdensity can decrease with increasing distance from the main magnet. Forexample, 3 detectors which are configured to receive signals can befastened on the room ceiling. An active position sensor can be, forexample, an optical transmitter, in particular, one or morelight-emitting diodes (LEDs), in particular infrared LEDs or anultrasonic transmitter. The acquisition apparatus can be, in particular,a 2D camera or a 3D camera and/or an optical position sensor, forexample, a position sensitive detector (PSD) sensor. In particular,three sensors can be provided wherein the sensors can be arranged in thecorners of a triangle. Alternatively or additionally, a plurality ofultrasonic receivers can be provided which are configured, inparticular, to calculate a position from ultrasonic signals received.The evaluation of the position can take place, in particular, by meansof trilateration. Trilateration can mean, in particular, that theposition is ascertained from a plurality of, in particular three,distance measurements. For example, a plurality of ultrasonic signalscan be used for measuring a plurality of distances from referencepoints, wherein the position can be ascertained from the plurality ofdistances. Alternatively or additionally, the evaluation of the positioncan take place by means of triangulation. During the triangulation, forexample, a distance between two base points can be known, wherein atriangle can be formed with a sought third position. If the anglesbetween the distance between the base points and the respective distancefrom the base points to the position are now ascertained, the positioncan be ascertained therefrom. For example, the angles can be determinedwith at least one, preferably a plurality of 2D cameras or 3D camerasand with infrared rays. A passive position sensor element can be, forexample, an optical retroreflector. A retroreflector is, in particular,an apparatus which reflects incident rays substantially independently ofthe angle of incidence and the alignment of the retroreflectorsubstantially in the direction from which the rays come. In particular,a rod can be provided at its end with a plurality of glass spheres whichare covered with silver. The glass spheres can each have, for example, adiameter of 20 to 200 micrometers, preferably from 40 to 160 micrometersand particularly preferably from 60 to 100 micrometers. The spheres canbe arranged, for example, on a carrier at the end of the rod. Forexample, the carrier can also have a spherical form. For example, theretroreflector can contain a pattern, for example, a CR code. A patterncan be advantageous, in particular, if a plurality of marker objects isused, wherein a distinction of the different marker objects can beenabled. The medical imaging system can comprise an illuminationapparatus with which the passive marker object can be illuminated, inparticular with infrared radiation. Reflected rays can be acquired, forexample, with at least one 2D camera and/or 3D camera. An independentposition sensor can be configured, in particular, to ascertain thecurrent position itself. The communication can take place by cable orwirelessly. In particular, the independent position sensor can comprisean ultrasonic transmitter and/or an optical transmitter, for example, aninfrared link or a lightguide that is configured to communicate theposition to the system. For example, the independent position sensor cancomprise a 3D Hall probe which can ascertain a position on the basis ofthe outer magnetic field, in particular in the longitudinal direction ofthe support. A 3D Hall probe can be used, in particular in a medicalimaging system which generates a magnetic field for scanning, forexample, a magnetic resonance tomograph. In this case, the magneticfield can decrease with increasing distance outside the acquisitionregion, which can be used for position determination. In particular, amethod or an apparatus as disclosed in the application DE 10 2016 203255 A1 can be used. Alternatively or additionally, the position sensorcan comprise an ultrasonic receiver, wherein a plurality of ultrasonictransmitters are arranged on the imaging system, for example, on amagnetic field-generating element or a magnet of the system. Theposition sensor can then receive ultrasonic signals of the ultrasonictransmitter and ascertain the position therefrom.

According to one aspect, it can be provided that an elongate depressionis arranged laterally and in the longitudinal direction of the supportand is provided with a touch sensor or distance sensor, in particular alaser sensor and/or an ultrasound sensor or with capacitive and/orresistive sensor strips for the measurement of a distance in thelongitudinal direction representative for the position to be acquired,wherein the marker object is introduced for determining the positioninto the depression and is registered by the distance sensor. Forexample, the user can move the marker object, in particular their handand/or a finger, into the lateral depression and thus interrupt orreturn a laser beam of the distance sensor or an ultrasonic wave ortrigger the touch sensor. For example, laser sensors or ultrasounddistance sensors can be provided with a measuring range of up to amaximum of 2.2 m to 3 m, preferably up to 2.5 m and a resolution of 0.5mm to 2 mm, in particular 1 mm. These values have proved to be a goodcompromise in practice, which relates both to a sufficient resolutionand also technical practicability and incurred costs. From a measurementof the distance from a reference position, the position in thelongitudinal direction or z-direction can be ascertained. On the basisof the feedback marking, the user can make fine adjustments to theposition of the marker object if the acquired position is not yetexactly the intended position. The capacitive and/or resistive sensorstrips can be arranged, in particular, along the depression. By means ofthe sensor strips, the position in the longitudinal direction can be, inparticular, acquired electrically. An acquisition in the depression canrepresent a solution that is particularly economical and/or easy toimplement, since the depression protects the distance or touch sensoragainst accidental triggering.

According to a further aspect, the subject and the support can beacquired and recorded with a 2D and/or 3D camera and displayed in avirtual environment, in particular, on a touch display, wherein themarker object is a finger, wherein the finger indicates the region to beexamined in the virtual environment. This aspect can advantageously beimplemented particularly well in existing systems since a touch displayis often already present there. The image recording of the subject cantake place, in particular, with an RGB sensor of the camera. In additionto the input of a position, a range, in particular a scan region can bespecified, for example, by circling with the finger. After the input ofthe position, it can be provided that the user inputs a command formoving the support into the acquisition region, for example, on thetouch display. According to one aspect, it can be provided thatinitially a general view of the subject is displayed, wherein after afirst input by the finger, the environment around the currently acquiredposition is displayed in an enlarged representation, wherein thefeedback marking is displayed both on the subject and also in thevirtual environment, in particular on the touch display, wherein theuser tests the position of the feedback marking and, if necessary,corrects it by means of a second input with the finger in the enlargedrepresentation in order to specify more exactly the region to beexamined. In particular, it can be provided that initially an image ofthe overall subject is displayed on the touch display and that aftertouching the touch display for position input of the image portion atthe touched site or around the touched site, is enlarged. In theenlarged image portion, a more exact position input or positioncorrection can then take place. It can be provided that a specified scanregion on the touch display, in particular in the vertical directionand/or the y-direction, can be displaced manually. For example, it canbe provided that a scan region is pushed into the subject. Alternativelyor additionally, it is conceivable that the scan region can also becorrected or finely adjusted after the movement of the support into thescan region or into the isocenter. For example, it can be provided thatafter the determination of the scan region or the FOV, the center of alocalizer, in particular a first localizer, coincides with the center ofthe FOV. For example, it can be provided that three standard slices, inparticular, a sagittal, a coronal and a transversal plane areautomatically scanned as soon as the support is at the determinedposition in the acquisition region.

According to one aspect, it can be provided that a field of view for ascan by the imaging system is determined on the basis of the position ofthe marker object and an offset in a sectional plane perpendicular tothe longitudinal direction of the support, wherein the offset isdetermined on the basis of the body region of the subject associatedwith the respective region, in particular via empirical values of theoffset and the size of the field of view. Empirical values can be based,for example, on recordings of previous scans and/or suitable tables. Thefield of view (FOV) can be used, in particular, to carry out a firstlocalizer or a first test scan. The first localizer can comprise, inparticular, a scan of the sagittal, coronal and transverse slices whichintersect at the position of the marker object corrected by the offset.Advantageously, a medical workflow can thereby possibly be acceleratedsince a manual input of the localizer is no longer necessary and/orsince the position of the localizer matches more exactly with theposition of the organ to be examined. In particular, rather thanextending through the isocenter, sagittal and coronal slices can extendthrough the position specified with the marker object (possiblyincluding an offset). The FOV can be defined, in particular, by means ofvectors and/or scalars. For example, a vector (x, y, z) can be providedwhich indicates the center of the FOV. This vector can be ascertained,in particular, from the acquired position. In order to specify the FOVmore exactly, in particular within the subject, at least one offset fromthe position can be calculated. In particular, the offset can consist oftwo offsets in the spatial directions (x, y) perpendicularly to thelongitudinal direction of the support (z-direction). Thereby, inparticular, the position can be displaced into the subject, inparticular vertically downwards and/or in the direction of the center ofgravity in the (x, y) plane. The FOV position can be made up of theacquired position of the marker object MP and the two offset directionsMPoffsetx and MPoffsety as follows:

FOV-Position=MP+MP_(offsetX) +MP _(offsetY)

where

MP_(offsetX)=(1,0,0)×RegionFactorX(MP)

MP_(offsetY)=(0, −1,0)×RegionFactorY(MP)

For example, an FOV normal can be a vector of length one or can be thevalue one, for example, defined in the transversal direction or thenormal (0,0,1). In addition, an FOV rotation angle can be used, inparticular, a scalar which gives the rotation, for example this valuecan be set to 0. Optionally, a size of the FOV, FOV-Größe(MP), can betaken from a table with predetermined values dependent on the respectiveposition of the marker object (MP). The tables can contain, inparticular, predetermined values for RegionFaktorX(MP),RegionFaktorY(MP) and FOV-Größe(MP), each dependent on the acquiredposition of the marker object MP. These values can depend on whichregion of the subject, in particular which body region of the patient,is selected or acquired. For example, a position on the abdomenaccording to the empirical values can require a deeper-lying andlarger-dimensioned FOV than a position in or on the shoulder.

According to a further aspect of the disclosure, a method is providedfor determining a field of view for a scan by the imaging system on thebasis of a position of a marker object which marks a region to beexamined in a subject, wherein the position has been determined, inparticular, according to one of the preceding examples, wherein thedetermination of the field of view is carried out by an artificialneural network, wherein the neural network comprises an input layer forthe input of input data which comprises the position of the markerobject and optionally a size, a weight, a sex and/or a positioning, inparticular the position and direction, of the subject, wherein theneural network comprises a plurality of covered layers, in particular 5to 10 covered layers, wherein the neural network comprises an outputlayer which outputs at least the offset and the size of the field ofview. All the features and advantages of the method for determining aregion to be examined can be transferred similarly to the method fordetermining a field of view and vice versa. In particular, the aspectsfor determining the FOV, in particular, in relation to the offset can beused. Advantageously, tables of empirical values can be used orimplemented as the basis or training data for the neural network.Advantageously, the neural network contains fully connected layers. Theneural network can comprise, for example, 5 to 50 neurons, preferably 8to 20 neurons in the input layer. Input values can be, for example, apatient height (in particular a value), a patient weight (in particulara value), a patient sex (in particular a value) a positioning (inparticular 2 values, specifically a position and a direction), a bodyregion to be examined (in particular as a numerically encoded value)and/or the position of the marker object (in particular 3 values,specifically the three spatial directions). With regard to the bodyregion to be examined, for example, a predetermined numbering system canbe provided, wherein a number is assigned to each of the body regionsthat are to be examined which are possibly examined in the known manner.This assigned number can then be, in particular, an input parameter. Forexample, the numbering can be 1=head, 2=heart, 3=knee, 4=left breast,5=right breast, etc. In particular, the input values can be theparameters necessary for a scan. The parameters necessary for a scan canbe designated scan protocols, in particular, in the case of an SHS-MRscan. Furthermore 2 to 30, preferably 5 to 10 covered layers can beprovided which preferably each comprise 150 to 1300 neurons. The outputlayer can comprise, in particular, 2 to 30 neurons, preferably 5 to 10neurons. Output values can comprise, in particular, the RegionFaktorX,the RegionFaktorY, the FOV-GrößeX, the FOV-GrößeY and the FOV-GrößeZ. Byway of the use of a neural network, a particularly exact input orascertainment of the FOV, in particular the first localizer, can beenabled. The numerical values specified with regard to the number of thelayers and neurons can enable a particularly good compromise betweencomputation effort and accuracy and reliability.

According to a further aspect of the disclosure, a method is providedfor training an artificial neural network for determining a field ofview for a scan by the imaging system on the basis of a position of amarker object which marks a region to be examined in a subject, whereinthe position has been determined, in particular, according to example20, wherein the neural network comprises an input layer, in particularcomprising 8 to 20 neurons, a plurality, in particular 5 to 10 coveredlayers, in particular each with 150 to 1300 neurons, and an outputlayer, in particular with 5 to 10 neurons, wherein during the training,dropout layers are used, in particular with a dropout rate of 3-5%,wherein the method comprises the following steps: (1) providing inputtraining data, wherein the input training data comprises the position ofthe marker object and, in particular, a height, a weight, a sex and/or apositioning, in particular, a position and direction, of the subject;(2) providing output training data which comprises data of an offsetfrom the position of the marker object and a size of the field of viewspecified manually by a user from the input training data; (3) trainingthe neural network with the input training data and the output trainingdata, in particular by means of back propagation; (4) output of thetrained neural network. All the features and advantages of the methodfor determining a region to be examined and the method for determining afield of view can be transferred similarly to the method for training anartificial neural network and vice versa. In particular, a feedforwardnetwork with back propagation can be used as a monitored learningmethod. The network can have a structure which corresponds substantiallyto the above described neural network. For example, one or more dropoutlayers can be provided with a dropout rate of 1% to 10%, preferably 3%to 5%. Training data can be, in particular, collected data fromlocalizer positions manually specified in previous scans.

According to a further aspect of the disclosure, a positioning system isprovided for determining a region in a subject, in particular a patient,that is to be examined, on a movable support of a medical imagingsystem, comprising an acquisition apparatus for acquiring the positionof a marker object in relation to the subject, a projection apparatusfor projecting and/or displaying a feedback marking at the acquiredposition on the subject, a computer unit, wherein the computer unit isconfigured to ascertain a scan position of the support on the basis ofthe acquired position, and a motor, wherein the motor is configured tomove the support, in particular, in the direction of its longitudinaldirection, wherein the computer unit is configured to drive the motorand to initiate a movement of the support into the scan position. Allthe features and advantages of the method for determining a region to beexamined, the method for determining a field of view and the method fortraining an artificial neural network can be transferred similarly tothe positioning system and vice versa. Preferably, the positioningsystem can comprise means for carrying out the steps of the method asdescribed above.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages and features are described in the followingdescription of preferred aspects of the subject matter according to thedisclosure, making reference to the accompanying drawings. Individualfeatures of the individual aspects can be combined with one another inthe context of the disclosure. Components corresponding to one anotherare each provided with the same reference characters.

In the drawings:

FIG. 1 shows a positioning system according to a first aspect,

FIG. 2 shows a positioning system according to a second aspect,

FIG. 3 shows a method according to one aspect of the disclosure, and

FIG. 4 shows a schematic representation of an exemplary neural network.

DETAILED DESCRIPTION

FIG. 1 shows a positioning system according to a first aspect of thedisclosure. The positioning system is, in particular, part of a medicalimaging system 1 which in this case comprises a magnetic resonancetomograph (MRT) with an MRT tunnel 20. A subject 3, in particular apatient, can be placed for the purpose of an examination, on a support2. In this case, the positioning system comprises a marker object 4 inthe form of a rod which can be used to indicate the position of a regionto be examined. The region can be acquired by means of a 3D camera 17and calculated by the computer unit 8. In order to generate a feedbackmarking 6—in the form here of a cross—a projection apparatus 7 is usedwhich herein comprises a laser 11 and a flat parabolic mirror 13 whichis held by a frame 14. The flat parabolic mirror 13 is arranged suchthat the laser 11 or the location of the beam generation on the laserlies at its focal point. The laser is rotatable by means of a motor 10in a horizontal plane which approximately corresponds to the plane ofthe frame 14. This is made clear by an arrow. A laser beam generated bythe laser 11 is now incident at a site on the flat parabolic mirror 13dependent on the rotation of the laser 11 and is reflected there.Therein, the reflected laser beam 12 is returned parallel to atransverse direction of the support 2 and is further reflected extendingsubstantially in the horizontal plane, until it is incident upon a flatmirror 15. The flat mirror 15 then reflects the laser beam substantiallyperpendicularly downwardly in the direction of the support 2 or thesubject 3. By means of a beam former directly in front of the laser 11,the laser beam is given a cruciate form which then appears on thesubject as an illuminating cross 6. In this aspect, the flat mirror isalso rotatable by means of a further motor 10 about an axis parallel tothe longitudinal direction L of the support (indicated by an arrow).Through this rotation, a displacement of the feedback marking 6 can takeplace in a transverse direction Q of the support 2. Alternatively, theposition can also be specified by means of a touch display 9 on which animage of the subject 3 recorded with the camera 17 can be displayed.

FIG. 2 shows a positioning system according to a second aspect of thedisclosure. This aspect differs from the first aspect, in particular, inthat in this case the projection apparatus 7 is a video projector 16,which is movable on a linear guideway 19 in the longitudinal directionL. The feedback marking 6 can be generated on the subject 3 with thevideo projector 16. In addition to the video projector 16, a camera 17is movable on the linear guideway 19. The movement takes place with theaid of a motor 10 and by means of a drive spindle mounted on the linearguideway 19 and/or by means of toothed belts (not shown) mounted on thelinear guideway 19. The motor 10 can advantageously be an MR-compatiblemotor which is configured, in particular, to be operated in a magneticfield. For example, this can be a pneumatic motor, an ultrasonic motoror a hybrid drive.

According to a further aspect, an elongate depression 18 is arranged onthe side of the support 2, in which the user can specify, by inserting afinger as the marker object 4, a z-position, which can be acquired bymeans of corresponding sensor systems. Additionally or alternatively,the position can also be specified directly on the subject 3 which canbe acquired, in particular, by the camera 17.

FIG. 3 shows a method for determining a region to be examined in asubject 3. The subject 3 can be, in particular, a patient. In a firststep 101, the region is specified by positioning a predetermined markerobject 4 in relation to the subject 3 by a medical technical assistant(MTA). The marker object 4 can be, for example, a hand-guided object,for example, a rod or a marker which is placed on the subject 3 or isfastened on the subject 3. Alternatively, the marker object can also bethe hand or finger of the MTA. The position of the marker object 4 isacquired in a next step 102 by an acquisition apparatus 5. Theacquisition apparatus 5 can be, for example, at least one camera. Theacquisition can however also be ultrasonically-based, wherein theacquisition apparatus 5 comprises one or more ultrasonic receivers. In asubsequent step 103, a feedback marking 6 on the subject 3 is indicatedat the currently acquired position, in particular by projection. Theindication or projection therein takes place with the aid of aprojection apparatus 7. The projection apparatus 7 can comprise, inparticular, a laser 11, the laser beam 12 of which is deflected with theaid of mirrors to the subject 3 or a video projector 16. In thefollowing step 104, a computer unit 8 then calculates a scan position ofthe support 2 on the basis of the acquired position, so that in the scanposition, the region to be examined is arranged in an acquisition regionof the imaging system. Finally, in a last step 105, the support 2 ismoved automatically into the scan position wherein the movement can takeplace, in particular, automatically with a motor.

FIG. 4 shows a schematic representation of an exemplary neural networkas can be used, in particular, for the method for determining a field ofview (FOV). The neural network is not shown completely in thisrepresentation for reasons of clarity. It consists of an input layer 21.In this input layer, the input data 22 comprising the patient height,the patient weight, the patient sex, a positioning of the patient andthe position of the region to be examined and optionally a number of thebody region to be examined (for example 1=head, 2=heart, 3=knee, etc.).The neural network further comprises a plurality of covered layers 23which also comprise some dropout layers with a dropout rate of between3% and 5%. The output layer 24 supplies exclusively the output data 25comprising offset factors for different spatial directions, inparticular for the x-direction and y-direction and the size of the FOVin the three spatial directions. The different layers of the neuralnetwork are fully connected to one another. The neural network canpreferably be trained with data used in previous scans.

1. A method for determining a region to be examined in a subject on amovable support of a medical imaging system, the method comprising: a)manually specifying the region by positioning a predetermined markerobject in relation to the subject; b) acquiring the position of themarker object by way of an acquisition apparatus; c) projecting ordisplaying a feedback marking by a projection apparatus at the acquiredposition on the subject, wherein the position of the marker object andthe acquired position are adjustable; d) calculating, by a computerunit, a scan position of the movable support on the basis of theacquired position, wherein in the scan position, the region to beexamined is arranged in an acquisition region of the medical imagingsystem; and e) automatically moving the movable support into the scanposition with a motor.
 2. The method of claim 1, wherein the feedbackmarking is generated with a laser arranged above the movable support,and a laser beam is diverted with mirrors such that the laser beam isincident at the acquired position at least substantially vertically onthe marker object.
 3. The method of claim 2, wherein the laser generatesthe laser beam with a beam direction lying in a horizontal plane, thelaser beam generated is incident upon a flat parabolic mirror, a focalpoint of the flat parabolic mirror coincides with a position of thelaser so that the laser beam is reflected a first time in the horizontalplane and perpendicularly to a longitudinal direction of the movablesupport, and the laser beam is reflected a second time by a flat mirrorarranged in the horizontal plane in front of the flat parabolic mirrorsuch that it is deflected vertically in the direction of the movablesupport.
 4. The method of claim 1, wherein the feedback marking isgenerated with at least one video projector arranged above and orientedtoward the movable support, and wherein a light projection apparatuscomprises a light source, a collimation optical system, an imageformation unit, and a projection optical system.
 5. The method of claim4, wherein the at least one video projector is movable on a longitudinalaxis parallel to the longitudinal direction of the movable support. 6.The method of claim 1, wherein the subject is monitored with a 3D cameraor a combination of a plurality of 2D and/or 3D cameras.
 7. The methodof claim 6, further comprising: determining, by means of the 3D camera,a height of the subject at the acquired position; and carrying out, by acomputer unit, a parallax correction of the feedback marking generated.8. The method of claim 6, further comprising: moving the camera on alinear axis parallel to a longitudinal direction of the movable support;recording, by the camera, different views of the subject; and assemblingthe different views into a 3D image.
 9. The method of claim 1, whereinthe marker object is a human finger, and a position of the human fingeris ascertained by means of a 3D camera.
 10. The method of claim 1,wherein the marker object is a hand-guided object, which includes anactive, passive, or independent position sensor.
 11. The method of claim9, wherein gestures with the human finger are used as a position inputfor the input of a field of view of a scan to be performed with the 3Dcamera or for communicating control commands with the aid of projectedoperating elements.
 12. The method of claim 1, wherein the marker objectcomprises an active, passive or independent position sensor, and forspecifying the region to be examined, is placed on a desired region andfastened there on the subject.
 13. The method of claim 12, furthercomprising: placing a warming blanket on the subject; and fastening themarker object on the warming blanket by means of an adhesive layer or bymeans of a hook and loop area.
 14. The method of claim 10, wherein theactive, passive, or independent position sensor comprises: anilluminated optical retroreflector or an optical transmitter, wherein atleast one 2D camera or 3D camera acquires the marker object, or anultrasonic or infrared transmitter, wherein a position of the positionsensor is ascertained by trilateration or triangulation, or a magneticfield sensor and a magnetic resonance device, wherein the position isdetermined via a strength of magnetic flux density at the magneticsensor, and the strength of the magnetic flux density depends on aspacing from the main magnet of the magnetic resonance device.
 15. Themethod of claim 1, wherein an elongate depression is arranged laterallyand in a longitudinal direction of the movable support and is providedwith a touch sensor or distance sensor, a laser sensor, or an ultrasoundsensor or with capacitive or resistive sensor strips for a measurementof a distance in a longitudinal direction representative for theposition to be acquired, and wherein the marker object is introduced,for determining the position, into the depression and is registered bythe distance sensor.
 16. The method of claim 1, wherein the subject andthe movable support are acquired and recorded with a 2D or 3D camera anddisplayed in a virtual environment on a touch display, and wherein themarker object is a finger, which indicates the region to be examined inthe virtual environment.
 17. The method of claim 16, further comprising:initially displaying a general view of the subject; displaying, after afirst input by the finger, the environment around the acquired positionin an enlarged representation, wherein the feedback marking is displayedboth on the subject and also in the virtual environment on the touchdisplay; and testing, by a user, the position of the feedback marking,wherein the position of the feedback marking is correctable by means ofa second input with the finger in the enlarged representation in orderto specify more exactly the region to be examined.
 18. The method ofclaim 1, wherein a field of view for a scan by the medical imagingsystem is determined on the basis of the position of the marker objectand an offset in a sectional plane perpendicular to the longitudinaldirection of the movable support, and wherein the offset is determinedon the basis of a body region of the subject associated with therespective region via empirical values of the offset and a size of thefield of view.
 19. A method for determining a field of view for a scanby the medical imaging system on the basis of a position of a markerobject which marks a region to be examined in a subject, wherein theposition has been determined by the method of claim 1, wherein thedetermination of the field of view is carried out by an artificialneural network, which comprises an input layer for an input of inputdata comprising the position of the marker object and a size, a weight,a sex, or a position and direction of the subject, wherein the neuralnetwork comprises 5 to 10 covered layers, and wherein the neural networkcomprises an output layer which outputs at least an offset and the sizeof the field of view.
 20. A method for training an artificial neuralnetwork for determining a field of view for a scan by an imaging systemon the basis of a position of a marker object which marks a region to beexamined in a subject of claim 19, wherein the neural network comprisesan input layer comprising 8 to 20 neurons, 5 to 10 covered layers eachwith 150 to 1300 neurons, and an output layer (24) with 5 to 10 neurons,wherein during the training, dropout layers with a dropout rate of 3-5%are used, wherein the method comprises: a) providing input training datathat comprises the position of the marker object and a height, a weight,a sex, a body region to be examined, or a position and direction of thesubject; b) providing output training data which comprises data of anoffset from the position of the marker object and a size of the field ofview specified manually by a user from the input training data; c)training the neural network with the input training data and the outputtraining data by means of back propagation; and d) outputting thetrained neural network.
 21. A positioning system for determining aregion to be examined in a subject on a movable support of a medicalimaging system, comprising: an acquisition apparatus configured toacquire the position of a marker object in relation to the subject; aprojection apparatus configured to project or display a feedback markingat the acquired position on the subject; a computer unit configured toascertain a scan position of the movable support on the basis of theacquired position; and a motor configured to move the movable support ina direction of its longitudinal direction, wherein the computer unit isconfigured to drive the motor and to initiate a movement of the movablesupport into the scan position.
 22. The positioning system of claim 21,comprising means for carrying out the steps of a method for determininga region to be examined in the subject on the movable support of themedical imaging system by: a) manually specifying the region bypositioning the marker object in relation to the subject; b) acquiringthe position of the marker object by way of the acquisition apparatus;c) projecting or displaying the feedback marking by way of theprojection apparatus at the acquired position on the subject, whereinthe position of the marker object and the acquired position areadjustable; d) calculating, by the computer unit, a scan position of themovable support on the basis of the acquired position, wherein in thescan position, the region to be examined is arranged in an acquisitionregion of the imaging system; and e) automatically moving the movablesupport into the scan position with the motor.